Horticulture Magazine

Ericaceous Compost

A gardener planting pink Hydrangea flower in ericaceous soil

If you want to grow acid-loving plants in your garden, then ericaceous compost provides an ideal environment for them to flourish.

You may have heard of ericaceous compost even if you’ve never used it in your garden. The pH balance of ericaceous compost makes it perfect for growing acid-loving plants.

Some of the most beautiful species of plants need acidic soil to thrive, so having ericaceous compost gives you the ability to add a wider variety of plants and shrubs to your garden.

Pink Rhododendron blooming flowers
Rhododendron love acidic soil!

Below is a full guide to ericaceous soil, including its benefits, the types of plants that need it, how to grow your own ericaceous soil and frequently asked questions.

What Is Ericaceous Compost?

Ericaceous compost is a type of acidic compost that’s used for growing specific types of plants.

These can include heathers (‘ericaceous’ is derived from the Latin name for heathers), camellias and rhododendrons but it can be used for pretty much any type of plants that don’t do well in alkaline soil.

What Are Its Benefits?

There are some great benefits of using ericaceous soil. These include –

  • Great for use with potted plants
  • Creates a perfect environment for acid-loving plants to flourish
  • Minimal feeding is required when good nutrients are used in the mix
  • Retains moisture very well
  • Is easy to make yourself

What Plants Need Ericaceous Soil?

There are many types of plants and shrubs that prefer ericaceous soil, including –

See a full list of 76 ericaceous plants in this guide.

When To Avoid It

Although ericaceous compost can be incredibly useful, there are times when it’s better not to use it.

Any plants that prefer alkaline soil, for example, would not be suitable for use with ericaceous compost.

Although ericaceous soil that’s only slightly acidic might not kill these types of plants, they won’t thrive in the same way as they would in alkaline soil.

Growing Potted Plants Using Ericaceous Compost

Ericaceous compost is excellent for use with potted plants for a few reasons.

Firstly, you can easily maintain the integrity of the compost when it’s not mixed in with other soil, as it might be in a garden bed or border.

Another big advantage to using ericaceous compost for potted plants is that you can grow them in the perfect position for them to thrive.

In most cases, acid-loving plants do best in light shade and kept out of direct sunlight, especially during the peak times of the day.

How Often Do You Need to Water & Feed Plants in Ericaceous Soil?

Although ericaceous compost typically maintains moisture well, this doesn’t mean you’ll never need to water plants that are in it.

A lot of ericaceous plants have shallow roots, meaning they can quite easily dry out during prolonged dry spells.

Therefore, it’s very important to keep the soil moist during dry spells by watering regularly.

It’s also vital to water any ericaceous plants when you’ve first planted them to ensure the bud survives.

When watering plants in ericaceous compost, it’s worth noting that regular tap water is usually alkaline, so using it on them could easily neutralise the soil.

To avoid this, it’s usually best to collect rainwater to use exclusively on ericaceous plants.

As for feeding, it’s always a good idea to use a good fertiliser if you want your plants to thrive.

You can buy plant feed that’s specifically designed for ericaceous plants and it’s certainly recommended you use this since it will contain all the required nutrients for your plants to flower at their best.

A lot of the most popular ericaceous plants flower during spring and summer, so this would be the best time to feed them.

How To Make Ericaceous Compost

Although there are plenty of places you can buy ericaceous compost, it’s quite easy to make it yourself. It mostly comes down to making the soil more acidic than it is alkaline.

To do this you can add things like pine needles, citrus peels and leaf mould to your existing compost mix.

Another way to increase the acidity of a compost mix is by adding sulphur chips to it. [source]

It’s important to note that when you’re making your own ericaceous compost, you won’t be able to add anything that might neutralise the pH of the compost, such as calcium or lime.

You’ll want to regularly test the pH levels of your compost to ensure that the right level of acidity is maintained.

This is particularly important when you’re adding ericaceous compost on top of regular soil since it will lose acidity over time.

Regularly adding new acidifying materials will help to ensure that the soil stays at a very high level of acidity.

It’s also a good idea to add a layer of mulch.

How To Acidify Regular Garden Soil

If you want to acidify your existing garden soil rather than making your own ericaceous compost, then this is quite easy to accomplish.

You can simply add sulphur powder to the soil until it reaches the level of acidity you require.

In order to know how much sulphur powder to use, you’ll need to know the current pH level of the soil you’re adding it to.

Because sulphur powder is very fine, you’ll want to add it to your soil when the weather is mild.

It’s also important that you wear the right safety equipment when using sulphur power. You should always wear safety goggles, a dust mask and gloves when you’re applying it.

Frequently Asked Questions

What is the pH of ericaceous compost?

Ericaceous soil doesn’t have a set pH level since people use different mixes. However, being an acidic soil, it usually has a pH level somewhere between 4.0 and 5.0.

Can I use ericaceous compost on all plants?

Plants tend to be quite adaptable, which means they can survive even in conditions that are less than ideal.

That being said – if you want your plants to thrive, then using the best type of soil is vital.

Ericaceous compost is ideal for acid-loving plants so you should use it for them solely and use neutral or alkaline soil for other types of plants.

Do hydrangeas need ericaceous soil?

Hydrangeas can survive in most types of soil, but since they’re an acid-loving plant, they’ll thrive much better in ericaceous compost.

Do magnolias need ericaceous compost?

Magnolias prefer slightly acidic soil, so ericaceous compost would work well, although they can do well in any type of soil providing it’s not alkaline.

Is ericaceous compost good for roses?

Roses can tolerate slightly acidic soil, so anything that’s below a pH level of 5.0 would not be ideal.

Will pansies grow in acidic soil?

Pansies do well in soil that has a pH level of 5.8 and below, which means ericaceous compost would work well.

What happens if you don’t use acidic compost on plants that need it?

If you use alkaline soil on plants that need ericaceous soil, then they’re likely to develop yellow leaves and die.

The reason for this is that ericaceous plants require iron as well as other nutrients that they cannot absorb in alkaline soil.

If you don’t want to change the pH of the soil in your flower beds or borders, then you can always choose to grow ericaceous plants in pots.

What’s the best way to care for ericaceous plants?

If you want to grow ericaceous plants, then it’s necessary not only to use ericaceous soil but also ensure you plant them in the right place.

Most ericaceous plants should not be grown in direct sunlight as it will cause their flowers to turn brown.

This being the case, you should only plant them in flower beds if you have a spot that isn’t exposed to direct sunlight.

If you don’t, then you can grow them in pots instead. This will give you the freedom to place them in the perfect spot.

In addition to putting ericaceous plants in the right spot, you should also make sure to feed and water them well.

Is it better to buy ericaceous compost or make your own?

If you want to grow ericaceous plants, then you might be wondering if it’s better to buy ericaceous compost from a garden centre or to make your own.

There are pros and cons to both.

Buying it from a garden centre or online means you can choose from different types of compost, depending on the type of plants you want to grow.

Ericaceous compost can vary quite a lot, with different nutrients used in different mixes.

Making your own compost means you can control exactly what you put in it, which is always a big advantage. It’s also the eco-friendly option that helps to minimise waste.

How often should you test the pH level of ericaceous soil?

How often you should test the pH level ericaceous compost will depend largely on a where you use it.

If you put the ericaceous compost on top of regular soil, in a flower bed or border, then it can easily lose acidity over time, so you should test the pH of the soil quite regularly so you can add acidifying materials such as pine cones if you need to.

How can I maintain the pH level of acidic compost?

There are a few ways to maintain the pH of ericaceous compost.

Firstly, it’s a good idea to keep the compost separate from other soil. Doing this means you can much better control the acidity levels of the soil as well as getting more accurate readings when you do a pH test.

Another reliable way to maintain the acidity of the soil is by adding a layer of mulch on top of it.

You should also consider using a plant feed that’s specially formulated for use with ericaceous plants, as this will not lower the acidity levels and will allow your plants to thrive.

Lastly, you should never water plants in ericaceous compost using tap water if you want to maintain its pH level.

Tap water might be convenient to use but it can reduce the acidity levels of the compost due to being alkaline.

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